Claude Allègre passed away (1937-2025)
With Claude Allègre, we lose one of the founding fathers of the modern IPGP, a dynamic researcher, an academic convinced that research is an education in itself, and of the considerable role that the University must play in the community.
Publication date: 06/01/2025
Institute Life
Claude Allègre, a historic figure at the IPGP, passed away. Claude Allègre (1937-2025) played a central role in the development of geochemistry in France from the early 1960s onwards, and was instrumental in transforming the Institut de Physique du Globe de Paris, founded in 1921 by Charles Maurain, into a multidisciplinary Earth sciences institute of international renown.
Thanks to the support of physicist Yves Rocard from the École Normale Supérieure in Paris, who helped him obtain funding from the “Direction de la recherche et des moyens d’essais du ministère des Armée”, Claude Allègre set up his first geochemistry laboratory in 1963, along with two other accomplices, Marc Javoy and Gil Michard, whom he managed to bring on board. This laboratory, named the Louis Barrabé Laboratory in honor of his professor of applied geology at the University of Paris Faculty of Science, and housed in a disused factory in Saint Maur, became part of the IPGP in 1968 and was subsequently split into three laboratories. Claude Allègre’s team became IPGP’s “Laboratoire de Géochimie et Cosmochimie”, from which the two current teams “Géochimie des Enveloppes Externes” and “Cosmochimie Astrophysique et Géophysique Expérimentale” are partly descended. At the same time, thanks to the support of Michel Alliot, the first president of the University of Paris VII, Claude Allègre and his colleagues set about creating the “UFR des sciences physiques de la Terre“, a teaching department, the forerunner of the IPGP’s “Département de la Formation et des Etudes Doctorales”. Plate tectonics was taught here, the only one of its kind in France. It teaches a quantitative geology that soon attracts talent from physics and chemistry.
Claude Allègre’s scientific work is characterized by several major periods, corresponding to major advances in our understanding of the Earth’s origin, evolution and functioning. The development of the Rubidium-Strontium dating method with Jean Louis Birck enabled the IPGP to become the first French laboratory to receive lunar samples in 1971, first from the Soviet Luna missions and then from the American Apollo missions. This work helped establish the very old age of the lunar crust, and was followed by seminal work in cosmochemistry with Jean Louis Birck, Christa Gopel and Gérard Manhès, such as that on the age of the solar system and the Earth with the Uranium-Lead system, the global composition of the Earth reconstructed from that of primitive meteorites, the chronology of formation of the components of chondrites with the extinct radioactivity of Manganese 53, the discovery of large-scale isotopic anomalies in the accretion disk with Chromium isotopes.
The increasingly precise analysis of isotopic compositions (Strontium, Neodymium, Lead) led Claude Allègre’s team in the 1970s-1980s to identify reservoirs in the mantle characterized by different isotopic compositions, such as the Dupal anomaly (named after Bernard Dupré and Claude Allègre), which corresponds to regions of the lower mantle that have retained the signature of subducted sediments, and to date these reservoirs using radiogenic isotopes. This marked the development of a true chemical geodynamics, making use of the discoveries of plate tectonics and associating the geological structures and processes revealed by geophysics with different reservoirs identified by geochemistry in the mantle and crust. At the same time, Claude Allègre was a driving force behind the development of glass mass spectrometers (ARESIBO spectrometers, named after the four researchers behind them: Allègre, Reynolds, Signer and Baur) for isotopic analysis of rare gases (Argon, Neon and Xenon). Studies, notably with Thomas Staudacher, of noble gases in all kinds of mantle rocks, have also led to the identification of different reservoirs for volatiles. Box models allowed to quantify the fluxes between these different reservoirs and to reconstruct the evolutionary dynamics of the mantle and crust over the course of Earth’s history, as well as Earth’s outgassing history and the origin of the Earth’s atmosphere. The “Allegresque history of chemical geodynamics” imagined for Claude Allègre by his MIT colleague Nobuchimi Shimizu shows the importance of the work of Claude Allègre’s team in this whole scientific epic.
Back in the 1990s, Claude Allègre, with the help of Bernard Dupré, was keen to develop a geochemistry that would be useful for ecological issues. The idea was simple: to apply the isotopic tracers that had been developed to study the Earth’s mantle or the formation of the solar system to the habitat of humans: rivers, the atmosphere and the ocean. It was then that the IPGP became heavily involved in a large-scale national program (DBT: Dynamics and Budget of the Earth), organizing ambitious sampling campaigns on major rivers, first the Amazon and then the Congo, and systematically applying isotopic tracers (Strontium, Rare Earths, Lead, Osmium, Boron, etc.). This work, which in particular required considerable analytical progress, led to the publication of founding articles on a true “chemical potamology”, making it possible not only to trace the processes involved in the formation of the planet’s habitable layer (the critical zone), but also to trace the impact of human activity on biogeochemical cycles. This evolution of IPGP’s research themes has also led to the application of isotope tracing to the ocean, and to important work showing in particular the role of rivers and erosion in the isotope signal recorded by ocean sediments.
Claude Allègre has never carried out any scientific work on the Earth’s present or past climates. However, at the end of his scientific career, which was cut short by a heart attack in 2013, Claude Allègre, then Professor Emeritus at the IPGP, along with a handful of colleagues, adopted a climate change skeptic stance.
Claude Allègre was director of the IPGP from 1976 to 1986, and subsequently remained highly influential in IPGP affairs. At the start of his directorship, he was confronted with the La Soufrière volcanic crisis in Guadeloupe. Over the evacuation of 70,000 people from the island of Basse Terre, he came into sharp conflict with Haroun Tazieff, who had been appointed head of volcanological observatories by Claude Allègre’s predecessor Georges Jobert. The lessons of this crisis were gradually learned over the following years, with the IPGP and the Institut National des Sciences de l’Univers of CNRS working together to create the Piton de la Fournaise observatory on Reunion Island, to develop the three observatories (in Guadeloupe, Martinique and Reunion Island), and to organize the French volcanological community. The way in which the IPGP, INSU-CNRS and the French academic community (along with BRGM and IFREMER) have responded to the volcanic crisis in Mayotte since 2018 shows just how far we’ve come. Claude Allègre attracted to the IPGP young researchers he had spotted at conferences or during his many visits to American universities where modern earth sciences were developing. These young researchers changed the scientific dimension of the IPGP, bringing new approaches and disciplines to France (Vincent Courtillot in paleomagnetism, Barbara Romanowicz in seismology, Claude Jaupart in physical volcanology, Jean Paul Poirier in materials physics, Paul Tapponnier in tectonics, among others) and, by snowball effect, attracting brilliant researchers and students from France and abroad. In 1985, Claude Allègre set up a space studies department at the IPGP, which he appointed José Achache to head: the IPGP’s current successes in planetary seismology and space magnetism are a direct result. During his term of office, Claude Allègre also supported the development of high-performance computing in geophysics, led by Albert Tarantolla. In 1990, the IPGP acquired a “Connexion Machine”, followed by a second one in 1993, making it the only institute in Europe with such computing capabilities. Finally, in 1990, Claude Allègre was instrumental in turning the IPGP by decree into a “grand établissement d’enseignement supérieur et de recherche”, thus completing Charles Maurain’s vision of bringing together all research, observation and teaching activities in a single university institute with its own resources.
In addition to the IPGP, Claude Allègre was passionate about the university, which he felt should be at the heart of the national research system, and he was fond of pointing out that there can be no high-level science without high-quality university teaching BY and FOR research. Despite many upheavals, he put into practice many of his ideas, developed in particular in a remarkable book entitled “L’âge des savoirs” (The Age of Knowledge) published in 1993, first as leader of the Socialist Party’s group of experts, then during his first stint at the Ministry of National Education between 1988 and 1992, and during his term as Minister of National Education, Research and Technology between 1997 and 2000. In particular, he was responsible for the University 2000 plan, which involved decentralizing universities and creating regional offices, the U3M plan (state-region) to renovate universities, and the launch of the European harmonization process (ECTS system and Bachelor-Master-Doctorate organization), the creation of the Institut Universitaire de France (IUF) to relieve teaching and research staff who wanted more time for research, and the “Loi Allègre” law on innovation and research (allowing academics to create start-ups) in 1999. Many of the ideas put forward by Claude Allègre and his teams (including members of the IPGP, in particular Laure Meynadier and Lydia Zerbib) have been taken up by subsequent ministers, in line with the general idea that tomorrow’s society is a knowledge society, and that the University must play a leading role in it.
Claude Allègre has received numerous distinctions for his scientific work, the most important of which are: the Goldschmidt Medal of the Geochemical Society in 1986, the Crafoord Prize (the “Nobel Prize for geologists”) shared with Gerald Wasserburg (Caltech) in 1986, the CNRS Gold Medal in 1994. Claude Allègre was a member of the US National Academy of Sciences (elected in 1985) and of the French Académie des Sciences (elected in 1995). He was Commander of the Legion of Honor, Commander of the Order of Academic Palms and Grand Officer of the National Order of Merit. True to the idea that scientists should not remain in their ivory towers (24), Claude Allègre is the author of numerous popular science books (more than 10), two of which have become classics and helped attract generations of students to the Earth sciences: L’Écume de la Terre in 1983 (The behavior of the Earth), which recounts the adventure of plate tectonics, and De la Pierre à l’Etoile in 1985 (From stone to star), which recounts the cosmochemical adventure of the 1970s to 1990s and the evolution of ideas on the formation of the solar system. He also published a treatise on isotope geochemistry in 2005.
Anyone who came into contact with Claude Allègre at the IPGP, in his laboratory, as a director of the IPGP, in the Physical Earth Sciences Department, or at major international conferences, will remember him as an exceptional man for the energy he exuded, the fascination he could arouse… as much as the rejection he could provoke. A man of strong character, he never shied away from speaking his mind, sometimes excessively, but it’s clear that the many projects he launched led to considerable progress. He was generous and protective of many colleagues. The first PhD students in his laboratory still have fond memories of Saturday morning group work meetings, the only quiet time for Claude Allègre when he could reflect on the week’s work. Demanding of himself and a hard worker, Claude Allègre was also demanding of those with whom he worked. Concerned with diversity and inclusion well before the term was coined, Claude Allègre was keen to promote gender parity, ethnic diversity and the integration of international students at the IPGP. Claude Allègre helped many people at one time or another in their careers to give new meaning to their research.
Claude Allègre invented a geochemistry that is not, as he liked to mockingly put it, “une géochimie du c’est pas pareil” (literally a geochemistry of “it is of a different kind”, meaning just comparing numbers without using models), but a science of processes and budgets that is a true reading of the Earth and the universe. He helped establish geochemistry as an indispensable discipline for understanding the Earth and its evolution in the Anthropocene, and was very proud to see that the tools and methods of geochemistry were spreading to other disciplines such as ecology, biology, forensics, history and, in the future, anthropology.
With Claude Allègre, we lose one of the founding fathers of the modern IPGP, a dynamic researcher, an academic convinced that research is an education in itself, and of the considerable role that the University must play in the community.
Marc Chaussidon and Jérôme Gaillardet
